[PATCHv8 18/26] v4l: add buffer exporting via dmabuf
Hans Verkuil
hverkuil at xs4all.nl
Wed Aug 22 04:41:05 PDT 2012
On Tue August 14 2012 17:34:48 Tomasz Stanislawski wrote:
> This patch adds extension to V4L2 api. It allow to export a mmap buffer as file
> descriptor. New ioctl VIDIOC_EXPBUF is added. It takes a buffer offset used by
> mmap and return a file descriptor on success.
>
> Signed-off-by: Tomasz Stanislawski <t.stanislaws at samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
> ---
> drivers/media/video/v4l2-compat-ioctl32.c | 1 +
> drivers/media/video/v4l2-dev.c | 1 +
> drivers/media/video/v4l2-ioctl.c | 15 +++++++++++++++
> include/linux/videodev2.h | 26 ++++++++++++++++++++++++++
> include/media/v4l2-ioctl.h | 2 ++
> 5 files changed, 45 insertions(+)
>
> diff --git a/drivers/media/video/v4l2-compat-ioctl32.c b/drivers/media/video/v4l2-compat-ioctl32.c
> index a2e0549..7689c4a 100644
> --- a/drivers/media/video/v4l2-compat-ioctl32.c
> +++ b/drivers/media/video/v4l2-compat-ioctl32.c
> @@ -971,6 +971,7 @@ long v4l2_compat_ioctl32(struct file *file, unsigned int cmd, unsigned long arg)
> case VIDIOC_S_FBUF32:
> case VIDIOC_OVERLAY32:
> case VIDIOC_QBUF32:
> + case VIDIOC_EXPBUF:
> case VIDIOC_DQBUF32:
> case VIDIOC_STREAMON32:
> case VIDIOC_STREAMOFF32:
> diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c
> index 71237f5..f6e7ea5 100644
> --- a/drivers/media/video/v4l2-dev.c
> +++ b/drivers/media/video/v4l2-dev.c
> @@ -607,6 +607,7 @@ static void determine_valid_ioctls(struct video_device *vdev)
> SET_VALID_IOCTL(ops, VIDIOC_REQBUFS, vidioc_reqbufs);
> SET_VALID_IOCTL(ops, VIDIOC_QUERYBUF, vidioc_querybuf);
> SET_VALID_IOCTL(ops, VIDIOC_QBUF, vidioc_qbuf);
> + SET_VALID_IOCTL(ops, VIDIOC_EXPBUF, vidioc_expbuf);
> SET_VALID_IOCTL(ops, VIDIOC_DQBUF, vidioc_dqbuf);
> SET_VALID_IOCTL(ops, VIDIOC_OVERLAY, vidioc_overlay);
> SET_VALID_IOCTL(ops, VIDIOC_G_FBUF, vidioc_g_fbuf);
> diff --git a/drivers/media/video/v4l2-ioctl.c b/drivers/media/video/v4l2-ioctl.c
> index dffd3c9..c4e8c7e 100644
> --- a/drivers/media/video/v4l2-ioctl.c
> +++ b/drivers/media/video/v4l2-ioctl.c
> @@ -458,6 +458,14 @@ static void v4l_print_buffer(const void *arg, bool write_only)
> tc->type, tc->flags, tc->frames, *(__u32 *)tc->userbits);
> }
>
> +static void v4l_print_exportbuffer(const void *arg, bool write_only)
> +{
> + const struct v4l2_exportbuffer *p = arg;
> +
> + pr_cont("fd=%d, mem_offset=%lx, flags=%lx\n",
> + p->fd, (unsigned long)p->mem_offset, (unsigned long)p->flags);
Why the unsigned long casts?
> +}
> +
> static void v4l_print_create_buffers(const void *arg, bool write_only)
> {
> const struct v4l2_create_buffers *p = arg;
> @@ -1254,6 +1262,12 @@ static int v4l_streamoff(const struct v4l2_ioctl_ops *ops,
> return ops->vidioc_streamoff(file, fh, *(unsigned int *)arg);
> }
>
> +static int v4l_expbuf(const struct v4l2_ioctl_ops *ops,
> + struct file *file, void *fh, void *arg)
> +{
> + return ops->vidioc_expbuf(file, fh, arg);
> +}
Not needed...
> +
> static int v4l_g_tuner(const struct v4l2_ioctl_ops *ops,
> struct file *file, void *fh, void *arg)
> {
> @@ -1947,6 +1961,7 @@ static struct v4l2_ioctl_info v4l2_ioctls[] = {
> IOCTL_INFO_STD(VIDIOC_S_FBUF, vidioc_s_fbuf, v4l_print_framebuffer, INFO_FL_PRIO),
> IOCTL_INFO_STD(VIDIOC_OVERLAY, vidioc_overlay, v4l_print_u32, INFO_FL_PRIO),
> IOCTL_INFO_FNC(VIDIOC_QBUF, v4l_qbuf, v4l_print_buffer, INFO_FL_QUEUE),
> + IOCTL_INFO_FNC(VIDIOC_EXPBUF, v4l_expbuf, v4l_print_exportbuffer, INFO_FL_CLEAR(v4l2_exportbuffer, flags)),
...use IOCTL_INFO_STD instead.
> IOCTL_INFO_FNC(VIDIOC_DQBUF, v4l_dqbuf, v4l_print_buffer, INFO_FL_QUEUE),
> IOCTL_INFO_FNC(VIDIOC_STREAMON, v4l_streamon, v4l_print_buftype, INFO_FL_PRIO | INFO_FL_QUEUE),
> IOCTL_INFO_FNC(VIDIOC_STREAMOFF, v4l_streamoff, v4l_print_buftype, INFO_FL_PRIO | INFO_FL_QUEUE),
> diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
> index 7f918dc..b5d058b 100644
> --- a/include/linux/videodev2.h
> +++ b/include/linux/videodev2.h
> @@ -688,6 +688,31 @@ struct v4l2_buffer {
> #define V4L2_BUF_FLAG_NO_CACHE_INVALIDATE 0x0800
> #define V4L2_BUF_FLAG_NO_CACHE_CLEAN 0x1000
>
> +/**
> + * struct v4l2_exportbuffer - export of video buffer as DMABUF file descriptor
> + *
> + * @fd: file descriptor associated with DMABUF (set by driver)
> + * @mem_offset: buffer memory offset as returned by VIDIOC_QUERYBUF in struct
> + * v4l2_buffer::m.offset (for single-plane formats) or
> + * v4l2_plane::m.offset (for multi-planar formats)
> + * @flags: flags for newly created file, currently only O_CLOEXEC is
> + * supported, refer to manual of open syscall for more details
> + *
> + * Contains data used for exporting a video buffer as DMABUF file descriptor.
> + * The buffer is identified by a 'cookie' returned by VIDIOC_QUERYBUF
> + * (identical to the cookie used to mmap() the buffer to userspace). All
> + * reserved fields must be set to zero. The field reserved0 is expected to
> + * become a structure 'type' allowing an alternative layout of the structure
> + * content. Therefore this field should not be used for any other extensions.
> + */
> +struct v4l2_exportbuffer {
> + __u32 fd;
> + __u32 reserved0;
> + __u32 mem_offset;
> + __u32 flags;
> + __u32 reserved[12];
> +};
OK, I realized that we also need a type field here: you need the type field
(same as in v4l2_buffer) to know which queue the mem_offset refers to. For
M2M devices you have two queues, so you need this information.
Is there any reason not to use __u32 memory instead of __u32 reserved0?
I really dislike 'reserved0'. It's also very inconsistent with the other
buffer ioctls which all have type+memory fields.
Regarding mem_offset: I would prefer a union (possibly anonymous):
union {
__u32 mem_offset;
unsigned long reserved;
} m;
Again, it's more consistent with the existing buffer ioctls, and it prepares
the API for future pointer values. 'reserved' in the union above could even
safely be renamed to userptr, even though userptr isn't supported at the
moment.
> +
> /*
> * O V E R L A Y P R E V I E W
> */
> @@ -2558,6 +2583,7 @@ struct v4l2_create_buffers {
> #define VIDIOC_S_FBUF _IOW('V', 11, struct v4l2_framebuffer)
> #define VIDIOC_OVERLAY _IOW('V', 14, int)
> #define VIDIOC_QBUF _IOWR('V', 15, struct v4l2_buffer)
> +#define VIDIOC_EXPBUF _IOWR('V', 16, struct v4l2_exportbuffer)
> #define VIDIOC_DQBUF _IOWR('V', 17, struct v4l2_buffer)
> #define VIDIOC_STREAMON _IOW('V', 18, int)
> #define VIDIOC_STREAMOFF _IOW('V', 19, int)
> diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
> index e614c9c..38fb139 100644
> --- a/include/media/v4l2-ioctl.h
> +++ b/include/media/v4l2-ioctl.h
> @@ -119,6 +119,8 @@ struct v4l2_ioctl_ops {
> int (*vidioc_reqbufs) (struct file *file, void *fh, struct v4l2_requestbuffers *b);
> int (*vidioc_querybuf)(struct file *file, void *fh, struct v4l2_buffer *b);
> int (*vidioc_qbuf) (struct file *file, void *fh, struct v4l2_buffer *b);
> + int (*vidioc_expbuf) (struct file *file, void *fh,
> + struct v4l2_exportbuffer *e);
> int (*vidioc_dqbuf) (struct file *file, void *fh, struct v4l2_buffer *b);
>
> int (*vidioc_create_bufs)(struct file *file, void *fh, struct v4l2_create_buffers *b);
>
Regards,
Hans
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